With the advent of a recognized need to minimize undesirable emissions in the power plant at both low and high power operation much attention had been given to burner designs which will assure combustion temperatures within the burner so as to produce a minimum of CO, NOx and unburned hydrocarbons in the exhaust at all power settings with a minimum of power loss. The worst problem is the unburned hydrocarbons and CO at idle and low powers.
Attempts at improving the combustion have inevitably resulted in more complex burner constructions particularly the multiple stage combustors in which combustion occurs in several discrete zones. These concepts generally lead to complex fuel injection systems at several locations in the burner. It is desirable to produce the desired mixing and circulation of the combustible mixtures within the burner with a minimum of extraneous elements within the burner structure and to produce the recirculation desired without mechanical obstruction to the flow of the combustible mixture within the burner.